magneto telephones, local batteries being
used for talking purposes. On the other hand, we may have
_common-battery_ switchboards, adapted to connect lines employing
common-battery telephones in which all the current for both talking
and signaling is furnished from the central office. In still another
way we may classify manual switchboards if the method of distributing
the energy for talking and signaling purposes is ignored. Thus,
entirely irrespective of whether the switchboards are adapted to serve
common-battery or local-battery lines, we may have non-multiple
switchboards and multiple switchboards.

The term _multiple_ switchboard is applied to that class of
switchboards in which the connection terminals or jacks for all the
lines are repeated at intervals along the face of the switchboard, so
that each operator may have within her reach a terminal for each line
and may thus be able to complete by herself any connection between two
lines terminating in the switchboard.

The term _non-multiple_ switchboard is applied to that class of boards
where the provision for repeating the line terminals at intervals along
the face of the board is not employed, but where, as a consequence,
each line has but a single terminal on the face of the board.
Non-multiple switchboards have their main use in small exchanges where
not more than a few hundred lines terminate. Where such is the case, it
is an easy matter to handle all the traffic by one, two, or three
operators, and as all of these operators may reach all over the face of
the switchboard, there is no need for giving any line any more than one
connection terminal. Such boards may be called _simple_ switchboards.

There is another type of non-multiple switchboard adaptable for use in
larger exchanges than the simple switchboard. A correct idea of the
fundamental principle involved in these may be had by imagining a row
of simple switchboards each containing terminals or jacks for its own
group of lines. In order to provide for the connection of a line in
one of these simple switchboards with a line in another one, out of
reach of the operator at the first, short connecting lines extending
between the two switchboards are provided, these being called
_transfer_ or _trunk_ lines. In order that connections may be made
between any two of the simple boards, a group of transfer lines is run
from each board to every other one.

In such switchboards an operator at one of the bo